The UK has announced an immediate ban on all visitors from Denmark over concerns a new Covid-19 strain which has spread from humans to mink.
UK nationals and residents will be able to return but must isolate for 14 days along with all members of their household.
Earlier this week, Denmark ordered its military to cull all of the country's 17 million mink after 12 people were infected with the mutated Covid strain.
Transport Secretary Grant Shapps announced the policy change at 2.18am on Saturday - less than two hours before the new rules came into effect.
He tweeted: "From 4am on 7 November, British Nationals or residents who are returning to the UK directly or indirectly from Denmark will need to self-isolate with other members of their household until two weeks have passed since they were last in Denmark."
He added: "This decision to act quickly follows on from health authorities in Denmark reporting widespread outbreaks of coronavirus in mink farms.
"Keeping the UK public safe remains our top priority."
Home Secretary Priti Patel tweeted: "In order to respond quickly and decisively to the latest coronavirus developments, visitors from Denmark arriving into the UK will not be permitted entry.
"British Nationals, visa holders and permanent residents who have travelled to Denmark in the last 14 days will need to self-isolate along with their household."
On Friday, the Department for Transport announced Denmark would no longer be on the UK's travel corridor list.
The new strain also reacted more weakly to human antibodies against normal Covid-19.
According to the Danish authorities there is no indication so far that the mink mutant causes more severe disease.